This invention relates to an imroved pressurized dispenser unit which can be used to dispense the contents by operating a valve that maintains the pressure within the container similar to an aerosol container. Specifically the invention relates to a dispenser in which the contents are maintained under pressure by using atmospheric pressure acting against a piston unit which closes the end of a container that has been evacuated.
Aerosol containers are and have been widely used to package many products which are conveniently dispensed as a spray or as a foam which results when the pressurized contents are released by the action of the valve on the dispenser. There are many drawbacks to the present aerosol units. One of these is the fact that a low boiling liquid such as a fluorocarbon must be dissolved into the cans contents to supply the pressure required for the unit to operate. In addition to the cost of such propellant material, which usually comprises at least half of the contents of the can, there is curent concern with the effect of the propellants on the environment.
Another substantial drawback in the present type of aerosol unit is the fact that the compatability of the various ingredients with the propellant must be carefully evaluated. In some instances the composition of the contents are such that a special propellant must be used or, alternately, the formulation of the contents must be altered in order for the aerosol package to be made. This adds substantially to the packaging cost as well as to the cost of development for a specific aerosol package. The instant invention uses the contents material in concentrate form and there is no propellant which eliminates the compatability requirement.
Aerosol dispensers containing fluids use dip tubes to connect the valve to the lower portion of the contents in order to remove most of the contents from the dispenser. This is not required in this new type of dispenser since the contents are pressurized up to the valve and there is no vapor space over the contents. The fact that there is no vapor space also provides another substantial advantage in that, unlike the conventional aerosol units, this one will dispense the contents in any position including upside down.
Alternatives have been proposed to the aerosol unit in which pumping devices are attached to the dispenser. These units have substantial drawbacks compared to the aerosol units in that the delivery of the contents are cyclical instead of continuous. In addition, the pressure level that can be applied to the contents is limited and the use of the pump units is fatiguing to the operator. Other problems such as leakage from the pumps and clogging of the delivery systems are frequent.
The instant invention is capable of maintaining the contents under a constant predetermined pressure which can be made whatever is required to properly dispense the contents. This pressure is determined by the dimensions of the various parts of the dispenser and their interrelationship. In this respect the instant invention is capable of packaging many materials which could not be handled by the propellant containing aerosol units. The absence of the propellant also eliminates the variability of pressure due to the temperature changes of the surrounding environment which frequently causes poor performance of conventional aerosol units, particularly at low temperatures. The absence of the propellant introduces a degree of safety to the dispensr of the instant invention. In conventional aerosol units at high temperature the propellant can generate very high pressures which may lead to rupture of the container in an explosive manner which is a dangerous condition. The instant invention does not pose this hazard. If the contents of the dispenser do not generate a great deal of volatiles at elevated temperatures, there is no explosion hazard. The vacuum surrounding the contents adds a positive safety factor by excluding air from the contents in the event that the contents are flammable.
There are conveniences in the filling operation which represent cost savings in the use of the instant invention. The container can be filled with simple measuring and filling equipment since it can be done under normal room conditions. The activation of the dispenser can be done immediately subsequent to the filling or it can be delayed to a later time so that the contents can be stored unactivated. This would have the advantage of safe storage since there would be no pressure condition to be concerned with. The packages can be activated at the time of shipment which would reduce the number of potentially defective units due to leaking valves or leaking seals that usually develop as a result of long term storage under pressure.
Another advantage of the invention is that it can make use of the existing technology of valves to dispense the contents of the dispenser which have been developed for the standard aerosol container. Other features such as flexibility in shape are also basic to the invention.